As @ypercube stated this seems to be a typo and should be changed to "more de-normalized schemas". One of the following paragraphsinthe Oracle manual states:
Snowflake schemas normalize dimensions to eliminate redundancy. That is, the dimension data has been grouped into multiple tables instead of one large table. For example, a product dimension table in a star schema might be normalized into a products table, a product_category table, and a product_manufacturer table in a snowflake schema.
This product dimension table of the star schema described here is not in third normal form but are results of joining (denormalize) some tables of the snowflake schema.
I found aricles on the web that describe why a star schema is not in 3rd normal form link link